Proper CUME to convert to One-World


We are getting ready go start the conversion to One-World. I am getting mixed reviews of which CUME level to be on.
Some folks say CUME 11 is fine but is more work to get One-World installed. Some say CUME 12 has some problems
but is less work to get One-World installed.

What experiences have folks had and which would you say is the better CUME level to be on?

We are V4R4M0, A7.3 cume 8.

Thank you for your help.